The mixing of detergent or other concentrates with a water stream commonly occurs in preparation for cleaning services within a commercial facility. During such mixing, the liquid concentrate is drawn from a source and mixed, via an eductor utilizing venturi action, with a diluent water stream to form the overall diluted detergent or other effluent mixture. The foregoing mixing function typically occurs within a wall mounted cabinet that houses one or more concentrate sources (i.e., bottles of detergent or other concentrate) and is connected to a water source. A dispensing hose is typically connected to the cabinet for dispensing the water-concentrate mixture effluent into a bucket or other receptacle.
A back-flow preventer is often utilized in dispensing systems to prevent any back-flow of the effluent mixture into the water source. A back-flow of the effluent mixture into the water source may occur if the water source incurs a reduction in pressure that falls below the static pressure existing within the output of the effluent mixture. Because it is desirable to keep water sources free from any back-flow contamination, fluid dispensers are often subjected to public regulations requiring that the dispensers utilize the foregoing back-flow preventers.
Prior art back-flow preventers for dispensing systems typically comprise a standard atmospheric vacuum breaker (AVB), or air gap or a safe gap eductors used in singularity (i.e., one-at-a-time) during dispensing operations. An atmospheric vacuum breaker, also known as a standard siphon breaker and used within the plumbing trades, is located upstream of any eductor and utilizes an air inlet valve (i.e., a float cup) that opens during any loss of fluid pressure from a liquid supply. The air inlet valve remains closed by the fluid pressure of the fluid supply. During any loss of such pressure, the air inlet valve opens the air inlet and closes the liquid supply inlet to prevent any back-flow of effluent from the eductor into the liquid supply.
Numerous disadvantages, however, are associated with using an AVB in combination with an eductor for high flow rate fluid dispensers, or any liquid dispenser for that matter. Besides being bulky and expensive, the usage of AVBs requires regular inspections, testing and certification to ensure that the device works properly and meets certain mandated functionality requirements. For example, contamination of the internal components of the vacuum breaker, as understood in the art, (e.g. mineral deposits on the float cup gasket or bonnet) may cause a loss of the seal between the float cup gasket and bonnet. Therefore, AVB manufacturers typically recommend that vacuum breakers be inspected periodically (at least monthly) for contamination and/or deterioration of the internal working components. Components should be cleaned or replaced as required.
Furthermore, the AVB, when utilized in combination with a hose-type dispenser, must be mounted at a minimum height or elevation, in relation to that of the discharge outlet of the dispensing hose, to meet various plumbing code and/or AVB manufacturer requirements. For example, the American Society of Sanitary Engineering (ASSE) Standard 1001 et seq. requires that an AVB be installed such that the AVB's critical level (CL), i.e., the extreme bottom of the AVB's body casting, is not less than 6.0 inches above the flood level rim of the fixture or appliance served. Standard 1001 et seq. of the ASSE further requires that equipment-mounted AVB's shall be installed in accordance with manufacturer's instructions and have a CL not less than 1.0 inch above the flood level of the fixture or appliance served. Furthermore, the Uniform Plumbing Code (UPC) Chapter 4 requires that potable water outlets with hose attachments be protected by an AVB installed at least 6 inches above the highest point of usage located on the discharge side of the last valve.
For dispensing systems utilizing a dispensing hose having a discharge outlet, the discharge outlet of the hose, when raised to an elevated position, thus constitutes either the “flood level” of the dispenser under the ASSE or the“highest point of usage” located on the discharge side under the UPC. Such limitations thus typically require that a dispensing system utilizing an AVB be located at a minimum height location, namely, not lower than highest point that the discharge outlet of a dispenser's dispensing hose may be raised. For example, where the discharge outlet of a dispensing hose may be raised to a height or elevation of 7 feet, the foregoing regulations would require that the AVB be located at an elevation or height of 7 feet 6 inches, i.e., 6 inches higher than that of the dispensing hose's discharge outlet. Whereas a dispenser utilizing an AVB is required to comply with such limitations relating to the location of the discharge outlet of the dispenser's dispensing hose, a dispenser utilizing an air gap or safe gap eductor need not comply with such limitations.
Thus, in seeking to avoid the use of AVB's, prior art backflow air gap and safe gap eductors have been utilized. Such eductors are used in singularity (i.e., one-at-a-time) during dispensing operations. Unlike atmospheric vacuum breakers (AVBs), air gap and safe gap eductors do not have to undergo regular inspections to ensure that they meet certain mandated functionality requirements. Furthermore, unlike AVBs. air gap and safe gap eductors do not have to be located at specific plumbing code-mandated height requirements in relation to the discharge outlet of the dispenser's dispensing hose. An air gap eductor utilizes a physical air gap separation between the liquid supply inlet and the eductor portion of the device. The separation distance (i.e., gap distance) is usually at least twice the inlet pipe diameter, but customarily not less than an inch. During fluid flow, pressurized liquid flows through the inlet, through and past the gap, and into the outlet leading to the eductor. Should the pressure of the incoming liquid supply drop while the air gap eductor is in operation, the mixed solution would be drawn backward from the eductor into the gap, with the physical air gap thereby preventing the liquid from flowing back into the supply inlet.
A safe gap eductor utilizes an elastomeric pipe interrupter between the liquid supply inlet and the eductor portion of the device. The elastomeric pipe interrupter typically comprises a rubber sleeve connected below the valve mechanism such that, when liquid is introduced into the top of the eductor, the sleeve expands against an outer tube having back-pressure escape holes defined therein. The expanded sleeve thus creates a conduit through which the liquid flows in a forward direction until a pressure reduction occurs at the liquid's inlet source. Should the pressure of the incoming liquid supply drop, the expanded sleeve collapses to expose the back-pressure escape holes of the outer tube. Any mixed solution drawn backward from the eductor thus exits into and through the escape holes of the outer tube instead of returning back into the rubber sleeve, thus preventing the liquid from flowing back into the supply inlet.
Nonetheless, certain disadvantages exist when attempting to utilize air gap or safe gap eductors in singularity in relation to high-flow-rate dispensers. For air gap eductors, such disadvantages are inherent in the geometry of the eductor itself. An air gap eductor requires that any liquid entering the eductor possess a minimal amount of force (i.e., velocity) to overcome the appreciable pressure that develops within the eductor's inlet. For closed eductors not utilizing an air gap, such a force is readily attainable through the manipulation of cross-sectional flow areas and pressures. However, because of the air gap present at the air gap eductor's inlet, pressure at the inlet will always be equal to a minimal, atmospheric pressure, thus requiring that the liquid crossing the air gap possess a substantial amount of force or velocity to enter the eductor. Because an increased force is generated through a decrease of cross sectional flow area, it may thus be difficult to achieve high volumetric flow rates through such a constricted area when the liquid source is at standard municipal service pressures of between about 30 psi and about 90 psi.
For safe gap eductors, such disadvantages are generally inherent in the construction of the eductor itself. Because the rubber sleeve of the elastomeric pipe interrupter is generally pressurized to close the back-pressure escape holes of the outer tube in ensuring that no liquid escapes while moving in a forward direction, the forward flow of liquid must undergo a reduction in cross-sectional flow area upon entering the sleeve to generate such pressure. This reduction of cross-sectional flow area thus undesirably restricts the flow rate of the eductor itself.
Furthermore, both the AVB-eductor combinations and single air gap eductor or single safe gap backflow preventers are inadequate for mixing two or more reagents with the diluent water stream to form an activated effluent mixture. For example, within the cleaning industry, chlorine dioxide (ClO2), an activated compound, is often utilized as an effective disinfectant for killing pathogenic organisms such as bacterial spores, legionella, tuberculosis, listeria, salmonella, amoebal cysts, giardia cysts, E. coli, and cryptosporidium. Due to its unstable nature, chlorine dioxide must be prepared immediately before use by mixing two reagents, i.e., sodium chlorite (NaClO2) with hydrochloric acid (HCl), with one another in water immediately before use. Because chlorine dioxide is a gas, it must be captured in a liquid at specific concentrations to remain stable. In desiring to maintain a stability of the mixture, it is thus ill advised to mix the two reagents prior to the mixture (i.e., the gas) being captured in water. Instead, it is preferable to dilute each reagent in water and thereafter combine the reagent dilutions to create the activated mixture.
The use of an AVB-eductor combination or single air gap or single safe gap eductor having two or more concentrate inlets for mixing the foregoing sodium chlorite and hydrochloric acid reagents is ill advised because of the unstable nature of the resulting chlorine dioxide gas mixture. This is because the inlet locations for the respective reagents on the eductor, in being proximal to one another within a high velocity water stream, provide an unstable environment for adequately mixing the reagents themselves with the water such that the resulting gas is carried within the water itself. The present invention overcomes the foregoing disadvantages and present numerous other advantages over the prior art systems.